What does it mean to derive state, and why is it better than syncing it with an effect?
Model answer
Derived values can be calculated from existing state or props during render, such as filteredItems from items and a search string, or fullName from first and last name. Storing them in separate state and updating them in useEffect adds extra renders and bugs when they get out of sync.
Calculate during render, and use useMemo only if the calculation is truly expensive.
Learn this topic
React useState Explained: Make Your Page React to Change in the course React.js Full Course: Beginner to Advanced.
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